Update restore-cluster documentation (regarding token updates)

[Dutchy-]

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At https://github.com/thelastpickle/cassandra-medusa/blob/master/docs/Restoring-a-full-cluster.md#case-2---restore-to-a-different-cluster-with-same-number-of-nodes it says:

Token ownership is updated on the target nodes to match the source nodes by passing the -Dcassandra.initial_token JVM parameter when the node is restarted. Which causes ownership to be updated in the local system keyspace.

However, this is no longer true, it does this instead: https://github.com/thelastpickle/cassandra-medusa/blob/3cea47c9de977f550015bfbc1715ebfcb5fd209a/medusa/cassandra_utils.py#L557

Source: https://the-asf.slack.com/archives/C0111B5KADA/p1648816330659049

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